The effect of haemodynamic stresses on endothelial permeability to macromolecules is
important to normal physiology and in the pathogenesis of atherosclerosis. I developed
and applied novel methods to evaluate effects on such transport of acute or chronic
exposure to flow along and across cultured endothelium. Porcine aortic endothelial cells
were isolated and cultured at passage 1-3 within the porous capillaries of a FiberCell
bioreactor. At confluence they were exposed to acute (4 h) or chronic (3-10 day) steady
or pulsatile luminal flow (mean shear 3.75 dyne/cm2), with or without transendothelial
flow (4 x 10-7 cm/s). Permeability to rhodamine-labelled albumin was assessed by
fluorimetry. Confluence of monolayers was confirmed by confocal and scanning
electron microscopy and by demonstrating established effects of vasoactive agents on
permeability: 10 U/ml thrombin increased permeability, as did 500 μM Nω-nitro-Larginine
methyl ester, compared to controls. Permeability was increased by acute
pulsatile shear and decreased by chronic pulsatile shear compared to static controls. A
decrease in PECAM-1 expression under chronic pulsatile flow was demonstrated by
flow cytometry. Steady flow gave higher permeability than pulsatile flow. The
introduction of transendothelial flow increased apparent permeability more than could
be explained by the addition of the convective transport itself. Preliminary studies
suggested that albumin transport may partially be an active process and demonstrated
the potential for engineered fibre walls that would allow effects of cyclic strain to be
investigated. In conclusion, the hollow fibre bioreactor allowed endothelial
permeability to be measured with or without exposure to luminal flow and
transendothelial flow over 30 days, permitting the investigation of effects of mechanical
stresses. Effects of shear stress varied with duration, pulsatility and direction relative to
the endothelial surface.Open Acces